This application is based on, claims the benefit of priority of, and incorporates herein by reference the contents of Japanese Patent Application No. 2001-359577 filed on Nov. 26, 2001.
1. Field of the Invention
The present invention relates to an ignition coil for an internal combustion engine and a method of manufacturing the ignition coil.
2. Description of the Related Art
Generally, high voltage is supplied to an ignition plug from a mechanical distributor through a high voltage wire. A recently developed method has been employed in which the high voltage is supplied directly from an ignition coil, placed separately in each cylinder of an engine, to the ignition plug. The independent ignition coils equip a coil portion, which has a primary coil and a secondary coil for a step-up from a primary voltage to a secondary voltage, and a high voltage tower portion, which impresses the high voltage generated in the secondary coil on the ignition coil through a high voltage spring. The coil portion and the high voltage tower portion are manufactured separately, and they are attached together in an assembling step. Finally, a gap in them is filled with a filling material such as an epoxy resin and the ignition coil reaches completion.
For example, in JP-A-11-186078 the structure of the electrical connectors between the coil portion and the high voltage tower portion is shown in FIG. 5 and is designed as such because of its simple manufacturing method. The structure of FIG. 5 consists of a secondary terminal 329, which is connected to a secondary wiring of a secondary coil portion, a high voltage terminal 339, which is electrically connected to the secondary terminal 329, and a high voltage spring 338 of a high voltage tower portion, which maintains contact with the high voltage terminal 339.
However, since the secondary terminal and the high voltage terminal are used as additional parts in the FIG. 5 structure, the manufacturing cost is high. Moreover, increasing the number of parts causes increased complexity in the manufacturing method and an increase in the number of manufacturing steps.
The ignition coil in this invention is broadly composed of a coil portion and a high voltage tower portion. The coil portion has a primary coil, which is a primary spool wound by a primary winding, and a secondary coil, which is a secondary spool wound by a secondary winding concentrically with the primary coil. The ignition coil also has a coil case in which is stored the primary coil and the secondary coil. The high voltage tower portion has a tower case under the coil portion and an elastic connection member that is placed in the center of the tower case and which contracts the end f the ignition plug. In the ignition coil, which impresses a supply voltage to the prim coil and to the ignition plug in the secondary coil, a secondary terminal is equipped in e lower end of the coil portion. The secondary terminal has a connection portion for connection with the secondary wiring and a contact portion to contact directly with the end o the elastic contact member.
The ignition coil can eliminate a terminal of the high voltage spring needed in prior ignition coils, while permitting manufacturing at a low cost and in a simple structure.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.